Well, how well it fares remains to be seen. Remember, these are not British made, so there is a lot in the wind here. The studs pulling out of the cases is certainly another area to worry about. All that extra pressure must be supported somewhere. Good luck.

Well, how well it fares remains to be seen. Remember, these are not British made, so there is a lot in the wind here. The studs pulling out of the cases is certainly another area to worry about. All that extra pressure must be supported somewhere. Good luck.

Yes, I understand the concerns, and appreciate your input.

We do have some examples to look at and see what can be done.I think that the 612 is a good example that this level of power can be reliably handled by the Bullet engine cases and studs.

From what I've seen, most of the stud breakages have come from people trying to cure oil leaks by tightening down the head nuts, when the problem is that the spigot is too tall, and stopping the head from compressing the gasket. So they tighten and tighten, and then snap the studs or pull the threads, and never do cure the leak.. The leak can only be cured by cutting down the spigot to the proper height. They could tighten the head till doomsday, and never cure the leak. And this is very common.

So, while the Indian-made studs and alloy may be suspect, they are not always the cause of these problems we see.But, for a person who is particularly concerned about this issue, it is not too difficult to install helicoils in the engine case, and install studs with higher tensile strength. That might give better peace of mind, and that's a perfectly fine way to address that issue.

And you are very right in pointing out that hi-performance modifications are not done in a "vacuum", and the stresses involved can affect other parts. This is part of the game, and people need to know this.

You know, Cyrusb, I'm guessing that old ACE MAY have done this once .... back in 1976 .... Hahaha!! You gotta remember that the old pig iron engine is way over-engineered for the maximum abuse on the muddy roads of old India .... I have faith .... !!

How can we go further?We can increase the breathing capacity of the intake and exhaust systems, going bigger than the 28mm carb might certainly help us, because our ports are 32mm, and that makes the carb a restriction.The whole idea is to get more air/fuel mixture in, which means sufficient volume, AND sufficient velocity,

The stock intake port is 32mm you say? So a 32mm mikuni would be quite realistic. With the free flow exhaust and filter would the torque/hp bands remain streetable with stock bore/stroke? I have also like your idea about refazing the intake cam a tooth in another thread you wrote about but would do this at a later date. In the meantime would a 32mm carb be fine on a iron barrel ? Been watching your tech posts a while, manny thanks on all your info. Gerry

How can we go further?We can increase the breathing capacity of the intake and exhaust systems, going bigger than the 28mm carb might certainly help us, because our ports are 32mm, and that makes the carb a restriction.The whole idea is to get more air/fuel mixture in, which means sufficient volume, AND sufficient velocity,

The stock intake port is 32mm you say? So a 32mm mikuni would be quite realistic. With the free flow exhaust and filter would the torque/hp bands remain streetable with stock bore/stroke? I have also like your idea about refazing the intake cam a tooth in another thread you wrote about but would do this at a later date. In the meantime would a 32mm carb be fine on a iron barrel ? Been watching your tech posts a while, manny thanks on all your info. Gerry

Hi Gerry,Yes, a 32mm carb is a good match for the stock Indian-made intake port.Since the port is already 32mm, you can increase the carb and manifold up to that size without reductions in torque, because the port is already defining air speed at its 32mm dimension. Sure, air might come thru a smaller carb at a higher speed, but then it just slows down at the 32mm port anyway. The iron barrel Bullet can use 32mm just fine.However, since the stock intake manifold is only about 28mm inside, it needs to be replaced or modified. Gasket too.Externally, the intake manifold mounting tube is about 33mm, so you can't realistically bore it to 32mm without leaving the walls too thin. So, boring it out completely, and then welding a piece of aluminum tube into it, with 1.25" I.D. and 40mm O.D. would be a good idea. Then you can just hone the I.D. open to the 32mm size to match the port, and have good wall thickness.The Mikuni 32mm flat slide has a round mounting tube which is 40mm.So, with a 40mm tube size on both intake mainfold and carb, you can use a straight rubber hose to match up well on both ends.If you don't do something with the intake manifold, then you have a 28mm restriction there, instead of at the carb, and the carb isn't going to do what you wanted.There's also a complete rubber manifold from Sudco which will be approximately the right size, which you can replace the entire intake manifold with. But, it's rubber, which is subject to tears and deterioration from the fuel, and I don't know how long they will last.

In the Mondello head, I have specified a 40mm O.D. alloy tube be permanently affixed to the head at the port entry, to take the place of the intake manifold, and it will be perfectly matched into the port as a port-extension that eliminates the need for a separate manifold and gasket.That will allow the port to be perfect from the carb into the engine, and will be as good as it can be. And eliminates any chances of mismatch or air leaks.However this type of mounting excludes bolted-flange carbs like the Amal, so this will be a head for use with Mikuni or Keihin type carbs that use rubber hose type mountings. The flat slide types are the carbs we have in mind, for performance reasons.

Of course, it would be recommended to support the carburetor with a bracket to the frame, so that the weight of the carb doesn't cause stress on the rubber hose, and make it fail early. Support the carb with a bracket, any time you have removed the stock air filter system and replaced the carb and filter that is unsupported on the "flying end". If you fail to bracket it, then it will make the rubber hose fail pretty quickly. Just a simple strut from the frame to the air filter hose-clamp will do. Simple and effective.

How about balancing? I too,May have done this before (although not to a bullet) and have never met an engine that did not benefit greatly from a good dynamic balance job. It can do two things, 1 increase output, 2 increase life.

CMW also sells the rubber manifold and alloy spacer for a 32mm carb. They were less expensive than Sudco when I called. The mounting flange is actually a Mikuni VM34/200 and is intended for a 32-34mm carb I do not know who makes the spacer.

How about balancing? I too,May have done this before (although not to a bullet) and have never met an engine that did not benefit greatly from a good dynamic balance job. It can do two things, 1 increase output, 2 increase life.

You are absolutely correct! Balancing will help out the old pig iron by not having it shake to bits as it runs - AND it will, indeed free up the ponies by NOT shaking everything to pieces ..... Of course, the harder you plan to spin it, the more critical that dynamic balancing becomes. This is probably NOT the case with my daily driver - I'll bet I never get it much over 3500rpm's .... !! I'm the guy you don't wanna be behind on the road!! Hahaha!!

How about balancing? I too,May have done this before (although not to a bullet) and have never met an engine that did not benefit greatly from a good dynamic balance job. It can do two things, 1 increase output, 2 increase life.

Yes, certainly! I agree.

Crank should be true, and balanced well for your set up.Bearings should be of good quality.The whole bottom end needs to be in best condition, if anyone considers making any significant power mods, and it can help a stock engine work better and longer too.

Perhaps I didn't emphasize this in my writing, and I should have.The bottom end needs to be able to take what you plan to throw at it, in terms of power.At this time, the European Performance Crankshaft assembly is the best available option, and is rock-solid.

At this time, the European Performance Crankshaft assembly is the best available option, and is rock-solid.

It is funny, but that single part costs almost half what I paid for my bike last year with only 600 miles on it. Fortunately I didn't see you indicating that it would be required with your secret project.

At this time, the European Performance Crankshaft assembly is the best available option, and is rock-solid.

It is funny, but that single part costs almost half what I paid for my bike last year with only 600 miles on it. Fortunately I didn't see you indicating that it would be required with your secret project.

Thanks again for your technical articles, Ace.

-Rick

Rick,The truth about the Bullet 500 bottom end is that it is reliable for long term in stock form, up to about 5000-5500 rpms, as long as it's made right and wasn't assembled with a hidden defect.Anything higher than 5500 rpm on a regular basis may have an effect of shortening the lifespan, or even having a catastrophic failure in certain circumstances.

I think if the stock rod gets a good inspection and polishing-out of any nicks and other stress-risers on the surface, and is a good example of the forging, it may be reliable to 6000 rpms, and I know of at least one successful Bulllet racer who runs his stock rods to 6000 rpm in races all the time, and they stay in one piece.But, that doesn't mean that ALL of them will do that, because of the spotty Indian quality control. And we must take that into account.

I targeted the 6000rpm redline for the stuff I'm making, because a PROPER Indian-made crank and rod should be able to get there without blowing up, ON OCCASION. I don't recommend making a habit out of it.I think that 5500 rpm is a much more "sane" rpm limit for street use with the stock bottom end, and perhaps even limiting it to 5250 rpm.I can't be certain of the quality of every single stock rod out there. And neither can anybody else.So, what I did was to pick an rpm range that could be of use to those who have both types of cranks and rods. The stock system, and the Performance Crank/Rod.The people with the Performance Crank have a very safe bet at 6000 rpm.The people who have stock cranks and rods have a more "iffy" proposition. But it is possible that good ones can do the full 6000 rpms.In any case, the power curve that I'm working on here is a wide one.You don't have to do 6000 rpms to get alot of power. It will do very fine with a 5500 rpm limit, or even less. So, each person can select how far up the rpm range he is willing to risk, for his personal use. It's his bike, and he can use it the way he wishes.But my recommendation would be to hold a stock bottom end down to under the 5500 rpm limit, and leave the full 6000 rpms to the guys with the stronger crank and rod.Or, at least don't go visiting the 6000 rpm redline as a frequent occurrence if you have a stock bottom end.I can't control the build quality of your bottom end. That's done at the factory, unless you do something to it to improve it. And I think that in some cases, the factory Indian made bottom ends can indeed withstand the 6000 rpm limits fairly regularly. But, I don't know which ones, or for how long.So, prudence would be good advice on this matter, and rev on the conservative side, unless you are willing to take risks.

However, if you wish to run like a racer, then it might be best to get the performance crank/rod system, or make regular tear-downs to inspect the integrity of your parts, just like the racers do.I am aware of the bottom end situation, and I didn't go there, frankly because I don't have enough money to be doing that right now. I have my efforts focused on the top end power production bits. There is a top-grade crank/rod system currently available already, although it is spendy. But it's good.If, at a later time, I may undertake some bottom end parts, then I can address that issue as I think best. But that is not for now. And I have to be realistic about what people have available to run with. So, I make rpm limit recommendations in the hopes that people don't blow up their engines.Some can take it, and some can't, and that's the "Enfield gamble".I provide the power parts, and it is the individual responsibility of the owner to ensure bottom end integrity to his own satisfaction, or his own risk.

I think that for someone who is serious about performance modifications, the Performance Crank/Rod assembly and a top-grade set of main bearings(not stock Indian ones), would be a pre-requisite.But it's not mandatory, if you are sensible about how far you go with the mods, and how you use it on the road. Be aware of the limitations of stock parts, because they are NOT racing parts.